The present application relates to a method of driving a GaN-based semiconductor light emitting element, a method of driving a GaN-based semiconductor light emitting element of an image display device using the method of driving the GaN-based semiconductor light emitting element, a method of driving a planar light source device, and a method of driving a light emitting device.
A GaN-based semiconductor light emitting element formed of a gallium-nitride (GaN)-based compound semiconductor may realize a light emitting wavelength from an ultraviolet ray to an infrared ray, by controlling band gap energy by a mixed crystal composition or film thickness thereof. In addition, a light emitting diode for emitting blue or green visible light from the ultraviolet ray is commercially available, and is used in wide application such as various display devices, illumination or inspection devices, or disinfection devices. In addition a bluish-violet laser diode is also developed and is used as a pickup for writing or reading of a large capacity optical disk.
However, in the GaN-based semiconductor light emitting element, when carriers are injected, the light emitting wavelength thereof is known to be shifted to a short wavelength side. For example, in a Light Emitting Diode (LED) in which an n-type GaN layer, an active layer formed of InGaN, and a p-type GaN layer are laminated, the lattice constant of InGaN crystal is slightly greater than that of GaN crystal. Accordingly, if the n-type GaN layer in which a top surface is a C plane, the active layer formed of InGaN in which a top surface is a C plane and the p-type GaN layer in which a top surface is a C plane are laminated, piezo spontaneous polarization is produced in a thickness direction of the active layer as the result of applying compression pressure to the active layer. As a result, in particular, if excitation strength is high, the light emitting wavelength from such an LED is shifted to the short wavelength side or a phenomenon such as deterioration of light emitting efficiency, increase of operating voltage, or saturation of luminance is generated.